CVE-2025-11385 is a buffer overflow vulnerability discovered in the Tenda AC20 router firmware up to version 16.03.08.12. The vulnerability arises from improper input validation in the sscanf function used in the /goform/fast_setting_wifi_set endpoint, specifically when processing the timeZone parameter. An attacker can remotely send a crafted request to this endpoint with a maliciously crafted timeZone argument that exceeds the expected buffer size, causing a buffer overflow. This overflow can corrupt memory, potentially allowing arbitrary code execution or denial of service on the device. The vulnerability requires no authentication and no user interaction, making it highly exploitable over the network. The CVSS 4.0 base score is 8.7, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and no privileges required. Although no active exploits have been reported in the wild, the public availability of exploit code increases the urgency for remediation. The affected versions include all firmware releases from 16.03.08.0 through 16.03.08.12. No official patches or mitigation links have been provided yet, emphasizing the need for immediate defensive measures.

The impact of CVE-2025-11385 is significant for organizations using Tenda AC20 routers as it allows remote attackers to execute arbitrary code or cause denial of service without any authentication or user interaction. Successful exploitation could lead to full compromise of the router, enabling attackers to intercept, modify, or disrupt network traffic, pivot into internal networks, or launch further attacks. This threatens confidentiality, integrity, and availability of organizational networks. Given the router’s role as a gateway device, exploitation could affect all connected devices and services, potentially leading to data breaches, service outages, and loss of trust. The high CVSS score reflects the broad scope and ease of exploitation, making this vulnerability a critical risk especially in environments relying on these routers for secure internet access.

1. Immediate mitigation should include isolating affected Tenda AC20 devices from critical network segments to limit exposure. 2. Monitor network traffic for unusual requests targeting /goform/fast_setting_wifi_set or anomalous timeZone parameter values. 3. Implement network-level filtering or firewall rules to block suspicious HTTP requests to the vulnerable endpoint. 4. Disable remote management features on the router if enabled to reduce attack surface. 5. Regularly check for official firmware updates from Tenda addressing this vulnerability and apply patches promptly once available. 6. As a temporary workaround, consider restricting access to the router’s management interface to trusted IP addresses only. 7. Conduct network segmentation to limit potential lateral movement if a device is compromised. 8. Educate network administrators about the vulnerability and ensure incident response plans include steps for this threat. These steps go beyond generic advice by focusing on immediate containment, detection, and access restriction until a vendor patch is released.